Spectrophotometry of Selected Regions of Europa—Revisiting Galileo NIMS Data

October 2025 • 2025PSJ.....6..237B

Authors • Belgacem, Ines • Cornet, Thomas • Buratti, Bonnie • Andrieu, François • Cruz Mermy, Guillaume • Schmidt, Frédéric • Mishra, Ishan

Abstract • Europa's surface is one of the most compelling mysteries of the solar system. It displays complex photometric behavior driven by its rich geology and interaction with the Jovian environment. Cryovolcanism across the surface creates frequent resurfacing, which is competing with external plasma and meteorite bombardment. This study revisits data from Galileo's Near-Infrared Mapping Spectrometer to conduct a comprehensive, multiwavelength photometric analysis of selected regions across Europa's surface. Using a Bayesian inversion framework and the Hapke photometric model, we estimate key surface parameters—including single scattering albedo, macroscopic roughness, and phase function properties—across three geologically diverse regions. Results show a significant link between macroscopic roughness and single scattering albedo, where values of θ¯ will sharply change when the single scattering albedo becomes too high (in this study, we found this transition to happen at ω ≈ 0.8). This is caused by multiple scattering that becomes too significant at a certain brightness and results in the illumination of shadows. This effect is potentially leading to systematic underestimation of roughness in traditional photometric modeling focused on the visible wavelengths. In addition, we observe increasing forward scattering at longer wavelengths, suggesting changes in internal scattering properties or composition. These findings highlight the need to account for albedo-driven photometric behavior in future analyses. This work is important to inform planetary data analysis in general but particularly for the planning of remote-sensing observations of the upcoming missions bound to the Jovian system—NASA's Europa Clipper and ESA's JUICE.

Links

• PDF https://iopscience.iop.org/article/10.3847/PSJ/ae057c/pdf
• ELECTR https://doi.org/10.3847/PSJ/ae057c